The Trump administration s new sanctions on Cuba include banning tourist travel, and cruise lines that previously stopped at the island are now scrambling to change their plans.

The restrictions announced Tuesday by the Treasury Department include a ban on cruise ship travel from the U.S., which became one of Americans most popular forms of leisure travel to the island after President Barack Obama lifted travel restrictions in 2016. The ships brought more than 142,700 people to Cuba within the first four months of this year, according to The Associated Press.

The travel restrictions went into effect on Wednesday, and the Treasury Department said those who have already purchased flight tickets or made other travel reservations wont be affected. But the announcement caught cruise lines off-guard.

We are disappointed that cruises will no longer be operating to Cuba, Adam Goldstein, chairman of the Cruise Lines International Association (CLIA), said Wednesday in a statement. While out of our control, we are genuinely sorry for all cruise line guests who were looking forward to their previously booked itineraries to Cuba.

CLIA, the biggest cruise industry trade association , said that the sudden change affects almost 800,000 passenger bookings that are either currently scheduled or already underway. Those bookings were made under a general license the U.S. government previously issued that authorized people to people travel to Cuba, according to the association.

Carnival Cruises said it has canceled visits to Havana and replaced them with another port, and is working to notify guests of their options for new itineraries. Guests who booked travel through the end of December can either remain on the same itinerary without a Havana stop and receive $100 per person, move to another itinerary and receive $50 per person, or cancel and receive a full refund.

Norwegian Cruise Line also posted a notice on its website about the travel restrictions. The line has ceased all trips to Cuba and is changing previously scheduled sailings. It has not released additional details but said, We thank our guests and travel partners for their patience as we navigate this unexpected, last-minute change.

Royal Caribbean International posted a notice saying it has secured alternative ports to the Cuban stops for its Majesty of the Seas and Empress of the Seas trips, and is in the process of contacting guests about the new itineraries.

For these guests, they will have the option of remaining on their sailing with the new itinerary and receiving a 50% refund or they may cancel their cruise and receive a full refund, the statement said.

The sanctions come in response to the Cuban governments support of Venezuelan leader Nicols Maduro. U.S. Treasury Secretary Steve Mnuchin said the restrictions will help to keep U.S. dollars out of the hands of Cuban military, intelligence, and security services.

There are about a dozen exceptions to the new restrictions, which would require a specific license and be determined on a case-by-case basis. Some of those instances could include family visits, official government business, journalistic activity, educational or religious activities, performances or athletic competitions, professional research and humanitarian work.